31 Jesus took the Twelve aside and told them, “We are going up to Jerusalem, and everything that is written by the prophets about the Son of Man will be fulfilled. 32 He will be delivered over to the Gentiles. They will mock him, insult him and spit on him; 33 they will flog him and kill him. On the third day he will rise again.”
34 The disciples did not understand any of this. Its meaning was hidden from them, and they did not know what he was talking about.
If you can’t explain it simply, you don’t understand it well enough.